Carbon dots from Guar Gum: Synthesis, characterization and preliminary in vivo application in plant cells

Microwave-assisted conversion of palm kernel shell biomass waste to photoluminescent carbon dots

“…Figure 2 shows the IR spectrum of PKS and CDs (sample A4, B5 and C1). For IR spectrum of PKS, it was noted that there are O–H stretching at 3381.1 cm −1 , C–H stretching (sp 3 ) at 2923.1 cm −1 , C=O stretching of carbonyl groups at 1735.5 cm −1 , C=C stretching (aromatic) at 1605.7 cm −1 and 1507.7 cm −1 as well as C–O stretching at 1040.4 cm −1 31 . The IR spectrum of A4, B5, and C1 CDs samples displayed the similar functional groups: hydroxyls (–OH stretching) and alkenes (–C=C stretching) at a stronger absorption intensity, an indication of the successful transformation of PKS into CDs with carbon core consisting of C=C elementary unit 20 .…”

“…Based on the IR spectrum of all sets of CDs, the functional group that contributed to characterization of CDs is oxygen-containing functional groups such as O–H, C=O and C–O–C stretching. These oxygen-containing functional groups found on the surface of the synthesised CDs most likely were derived from the oxidation of hydroxyl groups in PKS during carbonisation process, which played an important role in determining the photoluminescence intensity of CDs 20 , 31 . These functional groups would trap the excitons under excitation and the radiative recombination of those surface-trapped excitons.…”

“…Based on all the UV–Vis absorption spectra obtained, strong absorption peak at 280 nm along with a shoulder around 300 nm were observed. The peak at 280 nm was due to blue-shifted π − π * transition of the conjugated C=C groups from the carbon core 31 . Meanwhile, the shoulder was attributed to the n − π * transition of C=O groups (typical characteristic of fluorescent CDs) found on the surface of CDs 31 , 32 .…”

“…The peak at 280 nm was due to blue-shifted π − π * transition of the conjugated C=C groups from the carbon core 31 . Meanwhile, the shoulder was attributed to the n − π * transition of C=O groups (typical characteristic of fluorescent CDs) found on the surface of CDs 31 , 32 . According to the trends of UV–Vis absorption spectra, it can be said that the absorption intensity for set A and B increased when heating period was prolonged.…”

“…These showed that CDs synthesised from natural compounds or biomass are as competent as CDs fabricated from other sources. However, the simple synthesis (using water as the reaction medium) of CDs from biomass wastes tend to have low quantum yield due to incomplete carbonisation and the precursors lack functional groups (sulfur or nitrogen atom) for better luminescence property 20,[29][30][31][32][33][34] .…”